BS EN 1076-2009 pdf download.Workplace exposure— Procedures for measuring gases and vapours using pumped samplers — Requirements and test methods.
Do this whilst monitoring the concentration of the test substance behind the sampler with an instrument such as gas chromatograph equipped with a flame ionisahon or equivalent detector, an infrared spectrophotometer. etc. A suitable way of doing this is described in A, 1.
For substances with both long-term and short-term limit values, the breakthrough volume should be measured at a concentration of two times the short-term limit value especially if the ratio between the two limit values is
≥ 1.5.
For two-bed Type A sorbent tubes, use only the first (primary) bed or use specially prepared single-section tubes.
When it is not possible to monitor the concentration of the test substance behind the sampler using a direct reading instrument, breakthrough can be monitored using a back-up sampler that is changed and analyzed at regular intervals.
8.3.1.3.2 Chromatographic method
For porous polymers and similar chromatographic sorberits, instead of the procedure described in 8.3.1.3.1. the breakthrough volume can be predicted from the chromatographic retention volume. An example is given in Annex A.
NOTE 1 Breakthrough volume determined by the chromatographic method does not take into account relative humidity. Measurements by the direct method indicate that breakthrough volume at high t95 %) relative humidity is about a factor of two lower for porous polymers
NOTE 2 The chromatographic method is not suitable (or reagent impregnated sortients or activated carbon.
NOTE 3 The chromatographic method is not suitable for very high mass concentrations (more than 500 mglm’j.
8.3.1.4 Determination of the maximum air flow rate (only for Impregnated filters)
Repeat the test described in 8.3.1.3.1 for breakthrough volume at increasing flow rates up to a maximum of 50 % above the recommended flow rate using a minimum of three samplers at each flow rate setting. The breakthrough volume determined should be constant. Independent of flow rate As the experiment to determine the breakthrough volume is repeated at increasing flow rates a point could be reached where the breakthrough volume begins to decrease If the breakthrough volume drops by more than 5 % from its initial value the maximum air flow rate for the sampler shall be 90 % of the flow rate at which this occurs.
8.3.1.5 Determination of the minimum air flow rate (only for thermal desorption)
If a sampler is to be used at a low flow rate and an inlet restrictor is not used. perform the following test to establish the flow rate above which the effect of diffusion can be disregarded. If the sampler is to be used to measure a number of different substances carry out the test using the substance with the highest diffusion coefficient
Prepare six blank samplers and simultaneously sample a test atmosphere (set at about twice the limit value of the test substance). Use three of the samplers set at a low/moderate pump flow rate and three at zero flow rate, but with a pump still attached. Determine the mean mass of analyte retained on the three samplers set at zero flow. Subtract this from the mean mass of analyte on the samplers through which air was drawn to determine a corrected mass of analyte retained by these samplers. Use this mass to confirm the concentration of the test atmosphere. Having confirmed the concentration of the test atmosphere. use the mean mass of analyte retained by the three samplers set at zero flow to determine the diffusive uptake rate by these tubes in mI/mm. Multiply this value by 20 to determine the minimum air flow rate to be used with this type of sampler.
NOTE The level of the lowmoderate flow rate to be used depends on the dimensions of the sampler For example. for standard 4 mm to 5 mm bore. 6,4 mm outside diameter sorbent tubes with the sorbent bed set in the range from 12 mm to 18 mm from the sampling end of the tube. a flow rate of approximately 20 mI/mm is appropriate. For narrower sorbent tubes or sorbent tubes with the sorbent bed positioned further away from the sampling end of the tube. a flow rate of less than 20 mllmin is appropriate For wider bore sorbent tubes or sorbent tubes with the sorbent bed positioned more narrow to the sampling end of the tube, a flow rate of more than 20 mI/mm is appropnate
8.3.1.6 Storage after sampling
8.3.1.6.1 Direct method
Use two sets of at least six samplers and withdraw a known volume from a test atmosphere under the following exposure conditions.
— concentration. 0.1 LV and 2 LV
— time. recommended sampling time:
flow rate; recommended flow rate:
– relative humidity; (80 ± 5) %;
temperature: (20 ± 2) “C.
Analyze one set within one day and the other set after two weeks storage at room temperature, om as otherwise directed by the manufacturer
Calculate the mean for each of the two sets of test results and the difference between the means, in percent Compare with the requirement in 6314. If the requirement in 63.1 4 is not met repeat the test with a shorter storage time or by using different storage conditions.
NOTE An alternative approach can be to carry Out a more comprehensive set of experiments determining the recovery after a range of different storage times, for example. one day. three days, seven days, ten days and two weeks.BS EN 1076-2009 pdf download.
BS EN 1076-2009 pdf download
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